1. The Field of the Invention
The present invention relates to systems and methods for generating high voltage pulses. More particularly, the present invention relates to systems and methods for generating high voltage pulses controlled by solid state switches.
2. Background and Relevant Art
Many applications need a pulsed power supply that is able to deliver high voltage pulses. Spectrometers, accelerators, radar transmitters, high impedance electron guns, ion tubes, liquid polarizing cells, etc., are examples of applications that need high voltage pulses. In conventional systems, a pulsed power supply uses a high voltage pulse forming network and some sort of switch such as a spark gap or a thyratron.
These types of pulsed power supplies are often created using principles of Marx Generators. Generally, a Marx Generator is circuitry that generates a voltage pulse by charging a group of capacitors in parallel and then discharging the capacitors in series. FIG. 1 illustrates an example of a typical Marx Generator. In FIG. 1, a charging voltage 101 is applied to a pulse forming network 100. The stage capacitors 104 charge through the resistors 102 in a parallel fashion. The spark gaps 106 prevent the capacitors 104 from discharging into a load 108 until certain conditions are satisfied.
When the capacitors 104 are sufficiently charged, the lowest gap is typically allowed to break down or is triggered. When the lowest gap breaks down or triggers, two capacitors are effectively in series and the next gap breaks down. Very quickly, all of the gaps break down. The result of this process is that the capacitors 104 are connected in series and a voltage pulse is generated and delivered to the load 108. The capacitors 104 of a Marx Generator may also be charged using inductors or a series of transformers. In other example, the resistors 102 are replaced with inductors. The spark gaps can alternatively be replaced, for example, with switches such as thyratrons.
Because a Marx Generator is charged in parallel, the magnitude of the voltage pulse can be increased by adding additional charging sections. However, it has been found that the number of sections that can be stacked together is effectively limited by stray capacitance. As the number of sections in the pulse forming network increases, the stray capacitance to ground also increases. One of the effects of stray capacitance is that the current is diverted to ground. The stray capacitance also has an adverse affect on the rise time and/or fall times of the voltage pulse. The stray capacitance therefore limits the number of sections that can be included in the pulse generator.
The stray capacitance can also have an impact on the voltage that a particular section sees. In addition, the stray capacitance seen by one section is usually different from the stray capacitance seen by another section of the Marx Generator. Because the stray capacitance is not balanced across the sections of the pulse generator, some of the sections may experience higher voltages and may therefore malfunction. Although most systems are affected by stray capacitance, the inductors, resistors, transformers, and isolated supplied needed to charge the capacitors in the pulse generator also add stray capacitance to the pulse generator. In other words, the components of conventional pulse generators introduce additional stray capacitance to the system and further reduce the number of sections that can be successfully connected together.
Because Marx Generators are often used to generate high voltages, they can be quite large in both size and weight. In addition, a Marx Generator that generates hundreds of kilovolts should be using oil. Oil is typically necessary, but is often undesirable. Conventional pulsed power supplies or Marx Generators are often large and expensive, are limited by stray capacitance, and use components (such as thyratrons) that reduce their reliability.